GB2103030A

GB2103030A - Arranement for supplying electrical power to electronic devices arranged along a seismic streamer

Info

Publication number: GB2103030A
Application number: GB08222053A
Authority: GB
Inventors: Pierre Gonzalez
Original assignee: IFP Energies Nouvelles IFPEN; Compagnie Generale de Geophysique SA
Current assignee: IFP Energies Nouvelles IFPEN; CGG SA
Priority date: 1981-07-31
Filing date: 1982-07-30
Publication date: 1983-02-09
Also published as: CA1192984A; GB2103030B; IT8222585A1; IT8222585A0; NO160039C; DE3228526C2; FR2510831A1; FR2510831B1; NL8203036A; US4636992A; IT1152466B; NO822603L; JPS5866081A; JPH0224351B2; DE3228526A1; NO160039B

Description

1 GB 2 103 030 A 1

SPECIFICATION Arrangements for supplying electrical power to 65 electronic devices arranged along an elongate receiving assembly

This invention relates to arrangements for supplying electrical power to electronic devices arranged along an elongate receiving assembly.

An embodiment of the invention described hereinbelow is concerned with supplying electrical power to data aquisition devices arranged at regular intervals along a seismic streamer. Each acquisition device is operative to collect seismic signals generated by different receivers or groups of receivers disposed in adjacent elements of a seismic streamer, in response to echoes, from various reflecting or diffracting sub-soil layers, of acoustic waves generated by a seismic source, and sequentially to transmit said signals to a receiving and recording system disposed on a vehicle on receipt of appropriate commands. Arrangements of this type are described in UK Patent Application Publication No. 2 067 056A.

The electrical supply of the electronics devices contained in the seismic streamers may be effected, for example, by a d.c. voltage generator connected to the devices by electrical supply cables of great length. The electronic devices may be connected in parallel to the supply cables either directly or through transformers operative to transform the d.c. supply voltage to another d.c. voltage of lower amplitude.

This supply system has the disadvantage of ohmic losses through the supply cables, which are very often of great length, resulting in voltage drops which reduce the actual voltage supplied to the electronic devices connected to the cables at locations remote from the generator, in proportion to the length of the seismic streamer. Another disadvantage of a d.c. supply is the possible occurrence of electrolysis phenomena when moisture results in the condensation of water on electrical contacts.

The electrical supply of the electronic devices contained in the seismic streamer may also be effected by an a.c. voltage generator connected to electrical supply cables of great length. The electronic devices are supplied via a.c. voltage transformers having primary windings connected in parallel to the supply lines or cables. This type of supply arrangement also has the disadvantage, resulting from the impedance of the supply cables, of voltage drops which become higher as the length of the cables increases, so that the electronic devices of the seismic streamer which are at a great distance from the a.c. generator are liable to be insufficiently fed with electricity.

According to the present invention there is provided an arrangement for supplying electrical power to electronic devices arranged along an elongate receiving assembly in the form of a seismic streamer, the arrangement comprising a plurality of electrical supply assemblies associated with the respective electronic devices of the seismic streamer, each of said assemblies comprising three a.c. voltage rectifiers whose positive and negative output terminals are' respectively connected together and whose input terminals are connected respectively to secondary windings of three a.c. voltage transformers, corresponding primary windings of the transformers of all of the supply assemblies being respectively connected in series with three supply cables housed in the seismic streamer, the supply cables being connected to means for generating three currents which are out of phase with respect to one another.

The use of a current generator for feeding in series the primary windings of a plurality of voltage transformers makes it possible to maintain constant voltages at the terminals of said windings, irrespective of the number of interconnected supply assemblies. Accordingly, a very substantial lengthening of a seismic streamer fed by such a device may be effected without requiring any change in its supply system.

Moreover, the use of three-phase currents results in a decrease of the cable's overall impedance and of parasitic induction in seismic data transmisssion cables also located in the seismic streamer.

The invention will now be further described, by way of illustrative and non-limiting example, with reference to the accompanying drawing, wherein:

Figure 1 is a circuit diagram of a power supply arrangement embodying the invention, showing a supply assembly associated with each of a plurality of electronic devices distributed along the length of a seismic streamer, as well as supply cables connected to a current generator; and Figure 2 is a cross-sectional view of a preferred form of disposition of the supply cables inside the seismic streamer.

Figure 1 shows an electrical power supply arrangement comprising a three-phase current generator supplying currents 11=1 sin (ot, and 27r 12=1 sin (0)t+_) 3 47r 13 =1 sin (o)t±) 3 to supply cables 2, 3 and 4, respectively, connected to a seismic streamer having electronic devices distributed along its whole length. A respective supply assembly, one of which is shown at 18 in Figure 1, is associated with each electronic device. The supply assembly 18 comprises three voltage transformers 5,6, 7 having primary windings connected in series with the current supply cables 2, 3, 4, respectively. The generator 1 is operative to feed with cables with constant currents, irrespective of the number of voltage transformers arranged in series, whereby the voltage at the terminals of the primary 2 GB 2 103 030 A 2 windings is constant. Secondary windings of the three transformers 5, 6, 7 are connected, respectively, to input terminals of three rectifier bridges, 8, 9, 10. Output terminals + and - of the three rectifier bridges 8, 9, 10 are connected, respectively, to two terminals 11 and 12. The d.c. voltage between the terminals 11 and 12 is used to supply with electronic power the electronic device associated with the supply assembly 18.

The three supply cables 2, 3, 4 are placed (Figure 2) inside a seismic streamer defined by an external sheath 13. Usually, a plurality of conductor wires are necessary to interconnect different electronic devices in the form of data acquisition devices located at regular intervals along the seismic streamer. In such a case the streamer is also provided with three multiconductor cables 14, 15, 16 each comprising a plurality of conductors 17 surrounded by a shield 18 formed, for example, of a sheet of wire braiding. The different conductors 17 of the three cables 14, 15, 16 are used as transmission lines and the flexible shields 18 of the cables 14, 15, 16 form the supply lines or cables 2, 3, 4.

The use of the shields 18 of three multiconductor cables 14, 15, 16 to supply the electronic devices with three-phase current has the double advantage of reducing to a minimum parasitic induction between the transmission lines 60 and of avoiding the use of three special or specific conductors for conveying the electric current.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1983. Published by the Patent Office, 25 Southampton Buildings, London, WC2A l AY, from which copies may be obtained

Claims

1. An arrangement for supplying electrical power to electronic devices arranged along an elongate receiving assembly in the form of a seismic streamer, the arrangement comprising a plurality of electrical supply assemblies associated with the respective electronic devices of the seismic streamer, each of said assemblies comprising three a.c. voltage rectifiers whose positive and negative output terminals are respectively connected together and whose input terminals are connected respectively to secondary windings of three a.c. voltage transformers, corresponding primary windings of the transformers of all of the supply assemblies being respectively connected in series with three supply cables housed in the seismic streamer, the supply cables being connected to means for generating three currents which are out of phase with respect to one another.

2. An arrangements according to claim 1, wherein the supply cables comprise shields of three multiconductor cables disposed along the seismic streamer for transmission of said between said electronic devices and a central system.

3. An arrangement for supplying electrical power to electronic devices arranged along an elongate receiving assembly in the form of a seismic streamer, the arrangement being substantially as herein described with reference to the accompanying drawing.

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